1. Field of the Invention
The present invention relates to a vehicle lamp fixture used in, for instance, an automobile and more particularly to a vehicle lamp fixture in which a lens for transmitting and radiating light to the outside is fixed by welding to a reflector that reflects the light emitted from a light source.
2. Prior Art
In a vehicle lamp fixture, a lens is mounted on the front opening of a lamp fixture body or a reflector that has a light reflecting surface (the term xe2x80x9creflectorxe2x80x9d used in the following description includes a lamp fixture body); and so as to simplify the lamp structure and improve the sealability of the lamp, the lens is heat welded to the reflector. FIGS. 7A through 7C show one example of the process of heat welding for a vehicle lamp fixture.
In FIG. 7A, a reflector 101 that is formed of a thermoplastic resin has a reflector welding leg portion 106 on its opening edge. The reflector welding leg portion 106 has a convex cross section so that it protrudes towards the front. Also, on an inner surface of the reflector 101, a light reflecting film 105 is formed by way of surface finishing. The light reflecting film 105 is formed by laminating, for example, an undercoat coating film, an aluminum vapor deposition film, and a top coat coating film. However, the light reflecting film 105 is not formed on a tip end surface of the reflector welding leg portion 106.
On the other hand, a lens 107 is made of a transparent thermoplastic resin, and a lens welding leg portion 108 having a convex cross section that protrudes toward its own back surface is formed on a peripheral edge of the lens 17 so as to correspond to the reflector welding leg portion 106 of the reflector 101.
When the lens 107 is mounted on the reflector 101, as shown in FIG. 7B, a hot plate 113 is abutted against each tip end face of the lens welding leg portion 108 and the reflector welding leg portion 106, thus melting the tip end faces of the welding leg portions 108 and 106.
Next, as shown in FIG. 7C, each of the melted tip end faces of the lens welding leg portion 108 and reflector welding leg portion 106 are abutted and pressed together, thus heat welding the lens welding leg portion 108 to the reflector welding leg portion 106.
In some conventional lamp fixtures in which a lens and a reflector are welded in the manner as described above, the light reflecting film 105 is further formed on the tip end face of the reflector welding leg portion 106. FIG. 8A shows such a lamp fixture. In this lamp fixture, as shown in FIG. 8B, when the tip portion of the reflector welding leg portion 106 is melted and the reflector welding leg portion 106 and the lens welding leg portion 108 are welded, each of the resins of both welding leg portions 108 are 106 are not welded with a direct contact with each other. This occurs because the light reflecting film 105 remains between the abutting surfaces of the welding leg portions 108 and 106. As a result, the welding strength of both welding leg portions 108 and 106 is low, and the welded leg portions tend to easily be separated as shown in FIG. 8C.
Therefore, when forming the light reflecting film 105, it is important not to form the light reflecting film 105 on the tip end face of the reflector welding leg portion 106 as shown in FIG. 7A. For this reason, coating and vapor deposition are performed after putting a mask on the reflector welding leg portion 106 to cover it during the formation of the light reflecting film 105.
As seen from the above, in the conventional lamp fixture, the light reflecting film is formed in a complicated way, and the manufacturing costs thus tend to be high. Also, even when the light reflecting film is formed using a mask, coating material and vapor deposition film can flow under the mask through a gap between the mask and the reflector and adhere to the surface of the reflector welding leg portion. Thus, appropriate welding is not performed for this reason too.
In some cases, an aluminum film is formed as a light reflecting film by performing plating. In this case, a mask such as a resist is formed on the tip end face of the reflector welding leg portion. As a result, a process of peeling off of the resist film after the plating process is required. Thus, the process for forming the surface treatment film is complicated, causing high manufacturing costs.
Accordingly, it is an object of the present invention to provide a vehicle lamp fixture in which the assembling process is simple by reducing the number of production steps of a light reflecting film on a reflector, thus assuring low manufacturing costs.
It is another object of the present invention to provide a vehicle lamp fixture in which a lens and a reflector are welded securely to each other with a sufficient and appropriate strength.
The above objects are accomplished by a unique structure for a vehicle lamp fixture that comprises a thermoplastic resin reflector that has a light reflecting film formed on a surface and a thermoplastic resin lens that is welded to the reflector; and in the present invention, the reflector is provided with a reflector welding leg portion which has a convex cross section and to which the lens is welded to its tip end portion, and the tip end portion of the reflector welding leg portion is formed with an inclined surface which is inclined with respect to a direction in which the lens is welded.
In this structure, the light reflecting film includes a plasma polymerized film formed on the surface of the reflector. Also, the cross section of the inclined surface is, for instance, downwardly inclined from the central position toward both sides, respectively, in a width direction of the reflector welding leg portion, thus taking a triangular shape. In other words, the inclined surface has a V-shape or an angled letter C shape. Further, the angle of inclination of the inclined surface is preferably equal to or less than 60 degrees.
In the present invention, the inclined surface is formed on the tip portion of the reflector welding leg portion. In other words, an inclined surface having a triangular cross section is formed on the tip portion; and thus the tip portion is has an angled letter C shape surface.
Accordingly, when the tip portion of the reflector welding leg portion is heat melted by a hot plate, the light reflecting film automatically peels away while it changes its shape along the inclined surface, thus exposing the resin of the reflector welding leg portion on the tip portion. As a result, even when the lamp fixture body is entirely covered with a light reflecting film, it is possible to perform the welding of the lens and the reflector. It is thus also possible to obtain a lamp fixture that has an increased welding strength in the lens and the reflector and further to eliminate the need for a masking process that prevents the light reflecting film from forming on the tip portion of the reflector welding leg portion during the formation of the light reflecting film. The process for forming the light reflective film is simple, and the cost of the lamp fixture can be low.